The lateral extension of alumina scales as they grow at high temperature can induce substantial deformation of the substrate, especially under thermal cycling. The phenomenon is relevant to the understanding of failure mechanisms in thermal barrier coatings, and is explored here using model FeCrAlY substrates, bare as well as coated with electron beam physically vapor deposited (EB PVD) yttria-stabilized zirconia. Model surface imperfections consisting of shallow grooves experience significant distortions that evolve over time. The effect is most pronounced under cyclic oxidation, absent the thermal barrier coating (TBC). Distortions around the grooves are considerably reduced when the TBC is present.
A procedure for simulating thermally grown oxide (TGO) displacements has been used to predict the groove distortions. Those absent the TBC are shown to closely match those found experimentally for certain choices of TGO growth stress. It is also shown that the presence of an intact TBC entirely suppresses the distortions. Overlaying the simulated and measured TGO profiles absent the TBC reveals that, for consistency, the TGO growth stress should be lower on convex segments of the TGO than on flat segments, by about a factor 2.

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